04 July 2012

Diabetes Drug, Pioglitazone, May Cause Bladder Cancer

Diabetes is a disease where the body has an excess amount of sugar (glucose) in the blood stream. This has to do with how insulin, a hormone produced by the pancreas that regulates glucose levels, is treated by the body.

There are generally two kinds of diabetes: Type 1 and Type 2. In type 1 diabetes, the body produces little or no insulin to control blood sugar. With type 2, the body does not respond or resist the insulin produced.

Of the two, type 2 diabetes is the most common. 95% of diabetes cases in adults are of this type. It is associated with obesity, physical inactivity, and having a family history of diabetes.

With type 2 diabetes, the body has insulin resistance. Organs and tissues in the body such as the fat, liver, and muscle cells do not respond correctly to insulin. Insulin is needed to move glucose into cells, where it is stored and later used for energy. Without this process, the glucose starts to build up to high levels in the blood. This is called hyperglycemia.

If left untreated, hyperglycemia can cause damage to nerves, blood vessels, and other body organs. Chronic hyperglycemia injures the heart, even in patients without a history of heart disease or diabetes. It is also strongly associated with heart attacks and death in subjects with no coronary heart disease or history of heart failure.

There is no cure for diabetes and constant medication and insulin shots are required to keep the disease in check.

Some diabetes drugs may increase risk of bladder cancer

An increased risk of bladder cancer is linked to the use of pioglitazone, a medication commonly used to treat type 2 diabetes, according to a new study published in CMAJ (Canadian Medical Association Journal).

People with type 2 diabetes are at risk of several types of cancer, including a 40% increased risk of bladder cancer, compared to people without diabetes. Previous studies have shown a higher incidence of bladder cancer in people taking pioglitazone, a type of thiazolidinedione.
Video: FDA, Pioglitazone, and Bladder Cancer

To determine whether there is a link between pioglitazone use and bladder cancer, researchers conducted a systematic review and meta-analysis of randomized controlled trials and observational studies involving over 2.6 million patients.

"We observed an increased risk of bladder cancer associated with the use of thiazolidinediones," writes Dr. Jeffrey Johnson, School of Public Health, University of Alberta, with coauthors. "In particular, use of pioglitazone was associated with an increased risk of bladder cancer based on a pooled estimate from three cohort studies involving more than 1.7 million individuals."

The researchers also looked at a possible association with rosiglitazone, another type of thiazolidinedione, but did not see an effect.

"Although the absolute risk of bladder cancer associated with pioglitazone was small, other evidence-based treatments for type 2 diabetes may be equally effective and do not carry a risk of cancer," conclude the authors. "This study quantifies the association between pioglitazone use and bladder cancer and may help inform decisions around safer use of pioglitazone in individuals with type 2 diabetes."